Prostacyclin analogs (Iloprost, and others) have been used in the treatment of peripheral arterial occlusive disease (PAOD) for several years. Recent studies have documented benefit from intravenous as well as oral Iloprost in the treatment of ischemic ulcers and ischemic rest pain, setting the stage for a double-blind, placebo-controlled study to evaluate the safety and efficacy of oral Iloprost therapy in patients with severe PAOD.